Thermostat



Oct. 6, 1942. s. cRUM v 21,298,110 Y 4 THERMOSTAT I Filed April 11, 1940Fig. 4-

v hmmkn?- Sephen.. Crum- Patented Octi `6., 1942 UNITED STATE THERMOSTATstephen cram.. mnneipnua man.,

Regulator Minneapolis-Honeywell Minneapolis, Minn., a corporation ofDelaware adgnor to4 Company.

Application April 11, 194s, serial No. 329,121

z claims. (ci. zar-1s) The present invention relates to a compensatedcondition responsive element, and more particularly to such an element,and the construction' thereof, which is compensated vfor angularmovement.

Condition responsive devices, particularly biof metals having highexpansion oeilcients, and the strips 2| and 23 have low coefcients.

It is a well known fact that bimetal helices expand and contract axiallyand wrap and unwrap in response to'temperature changes. It

is alsowell known that, up to a certain angle Ior metallic elements, areoften wound into helices and utiliedv to rotate control devices uponchanges temperature. Many devices cannot be readily adapted to the useof rotary motion, v and still others could not possibly use it.

An object of the present invention is to provide a simpliiiedtemperature responsive element for obtaining straight line motion.

Another object is to provide a compact elemen as set forth in thepreceding object which is formed of bimetallic helices. A further objectis to provide a plurality of suitably mounted bimetallic helices whichare oppositely wound as to angular direction and exterior or interiorposition of the diierent metals of the bimetallic helices to therebyobtain a thermal element which will expand and contract axially and he'compensated `for rotary motion.

Other objects will be apparent in the accom- Y variation to which thehelices I0 and ii are suh-y jected because cf this pitch, Vthere willbefsubil will unwrap and elongate, thus moving the Y panyingspecification and the appended claims.

In the drawing: l

Fig. l is an elevational view of one form of my device, Fig. 2 is a viewlooking at the right-hand end .of Fig. 1,

Fig. 3 is an elevational view of a second form of my device, and v Fig.4 is a view looking at the right-hand end of Fig. 3.

' .Referring now more in detail to the drawing. in Fig. 1A a bimetallictemperature responsive element for practical purposes is shown as com-;prising bimetal helices generally indicated at III and Ii. The helicesili'and Il are fastened together at i2 by a rivet i3.' The helix it hasa mounting end il which is provided with a screw hole i5 by which theentire element may be `mounted to a suitable support. The helix Il has amotion takeoi! end Il which has a screw hole l i1 which may receiveascrew to secure a suitable takeoil device. 1

The two helices Il andli are eachcomposed of two metals having dierentexpansion coeiilcients. yAs shown in Fig. 2, the helix i! has aninternal strip 2B and an external strip. 2i.

'I'he helix Ii has an external strip 22 and an internal strip 23. Forpurposes of illustration,

it may be assumed that the strips 2l and V22 are' pitch, the axialmovementv is increased as -the pitch is increased.

YThe convolutions of -the are shown as being spaced from each other. Inother words, the angle'of the. pitch of these convolutions is quitegreat. Upon a temperature stantial axial movement of these helices as-well las rotative or angular movement thereof.

.Asinning now that the device is suitably moimted by the mounting end iland there is a temperature rise towhichthe device is subjected.Because'the strip 20 has a higher coeilicient of expansion than' thestrip 2i, the helix end I2 toward the right. Because the strip 22 has ahigher coelclcnt oi expansion than strip 2l, the helix Ii will wrap upand shorten, thus moving the motion takeo end i6 toward the right.Therefore, because the ends joined at i2 were also moved toward theright by the helix il, the movement of both helices-lli and Il is addedto eet a substantial axial movement of the end AII. When the helix Iiiexpands to move axially due to its right-hand wind, there is also.

an imwrapping rotation thereof. When the helix il contracts to moveaxially due to its lefthand wind. there -ls a wrapping rotation thereof.

-Hencaitissemthatthetwo helices Il an'd Il will rotate onposltely. Byproperly selecting 'the helices Il vand Il any eilective tationthereoimi! be completely compensated.- with lthe re 14o suit that only axialmovement will be taken ofi at the end il. Upon cooling, exactly thereverse o! the above dcribed action is eilected. It will be obviousthatthe siz'lps 20,22 and 2l, 23 could be reversed without altering thepractical oper,-

# ation o! the .device except to reverse the movement.

Referring now to Fig. 3, La temperature responsive element is shown ascomprising a righthand woimd bimetal helix 3 0 and a left-hand woimdbimetal helix Il. The helices-3l and Il are secured'together at n by arivet 33. 'The helix Il has a molmting end 3l in which there is v ascrew hole 3i which may receive a screw to suitably mount the -entirethermostatic element.A Thehelix has amotiontak'eoi! end 3i inwhich twohelices in and n a hole 31 is provided to which a takeo device may besecured.

The helices 30 and 3| are each made of metals having differentcoefcients of expansion. Referring to Fig. 4, the diierent strips ofmetal I and 4| are clearly shown. For purposes of illustration, it maybe assumed that the strips 40 are of high expansion material and thestrips 4| have a low coeilicient of expansion.

Upon a temperature rise, the high expansion metal 40 will expand at agreater rate than the low expansion metal 4| to thereby cause the end 32of the helix 3| to Wrap up and also to contract in length. The helix 30is also adapted to have its high expansion strip on'the outside so thatit also will contract when being heated. However, the strip 30 becauseit is right-hand wound,

whereas the strip 3| .is left-hand wound, will wrap up in the, oppositedirection, and in an equal amount to which the helix 3| is rotated.Therefore, it is seen that an element is provided in which similarexpansive metals are wound on the` exterior of both helices but the'twohelices have right and left-hand wound convolutions to therebycompensatefthe angular rotations of each, thus leaving only the additiveaxial movement of each to move a device. It will be obvious that Auponcooling of the entire sensitive element, just,the reverse of the abovedescribed action will be effected. It will also be understood that thesensitive metals, that is the high and low expansive metals, may bereversed in both of the helices without changing the mode of operationof the device.

' While I have shown two forms which my invention may take, it`wi11 beclearly understood that many modiiloations will occur to those skilledin the art. For example, it will be readily apparent that the elementscould be formed from a singlejpiece of material rather than from twopieces secured together. Therefore I wish not to be limited by the formsshown and described but by the spirit of the appended claims.

I claim as my invention:

1. In a control element, in combination, a rst helicallyA wound bimetaladapted to expand and contract axially and rotate angularly upon achange in temperature, means for securing one end of said first bimetalto a support, a second helically wound bimetal also adapted to expandand contract axially and rotate angularly upon a change in temperature,Isaid rst and second bimetals being wound in opposite directions so thatthey will rotate oppositely in the same degree for a given change intemperature, said bimetals4 being in axial alignment one within. theother, one end of the second bimetal being secured to the free end ofsaid rst bimetal Whereby the other end of said second bimetal will movein a straight line on temperature changes.

2. A device of the character described comprising, a first bimetal helixcoiled in a right-hand direction having its high expansive metal on theoutside to cause it to expand and contract axially and rotate angularlyupon changes in temperature, a second bimetal helix coiled in aleft-hand direction having its high expansivemetal on the inside tocause it to -expand and contract similarly to said rst bimetal but torotate angularly in an opposite direction to a similar degree, one ofsaid bimetals being arranged within the other bimetal, means securingsaid first and second bimetals together, mounting means at the distalend of said rst bimetal, and straight line motion takeoff securing meansat the distal end of said second bimetal.

STEPHEN CRUM.

